Degradation characteristics and effect mechanisms of estrogens during aerobic composting of chicken manure based on the orthogonal test.

Abstract

Environmental estrogens are currently a significant research topic, and poultry manure serves as a crucial source. This study investigated the degradation characteristics and effect mechanisms of six estrogens (E1, 17α-E2, 17β-E2, E3, 17α-EE2, and DES) during the aerobic composting of chicken manure. An orthogonal test comprising four factors (aeration rate, calcium-magnesium-phosphorus fertilizer (Ca-Mg-P fertilizer), coconut shell biochar, initial moisture content) and three levels of aerobic composting was conducted over a 45-day period to monitor the changes in estrogens and basic parameters. The results indicated that the factors influencing the estrogen degradation rate ranked as: initial moisture content (MC) > Ca-Mg-P fertilizer > aeration rate > coconut shell biochar. These factors significantly influenced the abundance of estrogen-degrading genera. Optimal composting conditions for estrogen degradation were identified as the addition of 10% coconut shell biochar, maintaining an initial moisture content of 60%, and using an aeration rate of 0.08 L min^-1∙kg^-1DM (dry matter), with an average degradation rate of 86.88% for the six estrogens under these conditions. During the composting process under various treatments, five known estrogen-degrading genera were observed with high relative abundance (max 31.08%), and the predominant genera were Staphylococcus and Brachybacterium for 17α-E2, 17β-E2, E3, 17α-EE2, and DES, and Pusillimonas for E1. The composition of microbial community structure changed significantly, and the dominated environment factors effecting the composition and succession of these genera were carbon to nitrogen ratio (C/N) and MC. The research results can provide both a theoretical basis and practical reference for the effective degradation of estrogens during the composting of chicken manure.